40 SUPPLEMENT TO THE CRAG MOLLUSCA. 



Pleurotoma robusta, S. Wood. Supplement, Tab. Ill, fig. 16. 



Spec. Char. PI. Testa ovato-fusiformi ; anfractibus 6,juxta suturam subangulatis, 

 longitudinaliter costulata, obsolete clathrata. 



Length, § ths inch. 



Locality. Upper Glacial, Bridlington. 



From a specimen in my own possession, given to me some years ago by Mr. Leckenby. 

 This is the largest species of that section of this genus, to which the generic name of Mangel 'ia 

 has been applied, that I have met with. The shell differs altogether from turricula in its 

 more robust form, in its greater size, and in the indistinctness of the shoulder angle. 



Pleurotoma turricula, Mont. Crag Moll., vol. i, p. 62, Tab. VII, fig. 13 ; Supplement, 



Tab. VII, fig. 8. 



Localities. lied Crag, Walton, Sutton, and Butley. Eluvio-marine Crag, Bramerton. 

 Chillesford Bed, Aldeby. Middle Glacial, Hopton. Upper Glacial, Bridlington (Wood- 

 ward). Post-glacial, March and Kelsea Hill. 



Several specimens of this well-marked and common British shell have occurred in the 

 Middle Glacial Sand of Billockby and Hopton, and I have a good suite of them from the 

 March gravel. It is rare in the Eluvio-marine Crag, and has occurred in the Chillesford 

 bed at Aldeby, and it is given as common at Kelsea Hill by Mr. Jeffreys. 



The specimen in Supplement, Tab. VII, fig. 8, is from the Middle Glacial Sand of 

 Hopton Cliff. It differs from the typical form of turricula (of which several individuals 

 have been obtained from the same sand) in the relatively greater proportion of the 

 body whorl, which is fully two thirds the length of the whole shell. As this, however, 

 seems to me only such a modification as might be expected to occur to a chance individual, 

 I have only ventured to regard it as a variety of PI. turricula. 



Pleurotoma assimilis, S. Wood. Supplement, Tab. VI, fig. 18. 



Localities. Red Crag, Butley. Middle Glacial, Billockby and Hopton. 



Spec. Char. PI. Testa ovato-fusiformi, obsolete clathrata ; longitudinaliter costulata 

 anfractibus sex,juxta suturam rotundato-angulatis ; spir a acuminata. 



Length, -j^ths of an inch. 



The specimen figured is from the Middle Glacial Sand at Billockby, and another has 

 occurred at Hopton. I have also found in the Red Crag of Butley a specimen of it quite 

 perfect, and of similar size to that figured, which, so far as I know, is unique in the Crag. 



